Since the advent of computer, people have been researching how to realize man-machine interaction in a more effective manner, i.e., man-machine interaction technology. The capacitive touch technology has improved the efficiency and convenience of man-machine interaction to a large extent by virtue of its advantages of direct, high-efficient, accurate, fluent, fashion and the like.
The projective capacitive screen comprises self-capacitor screen and mutual capacitor screen. The electrode array (which is made of Indium Tin Oxide, i.e., ITO, a transparent material) arranged in a horizontal direction and a vertical direction in a staggered manner can be manufactured on a surface of a glass substrate, and the horizontal electrodes and vertical electrodes constitute capacitors with the ground respectively. This kind of capacitor is a self-capacitor, i.e., the capacitor formed by the electrode and the ground. When a finger touches the capacitive screen, a capacitance of the finger would be added to the capacitance of the screen, and thus the capacitance of the screen would be increased.
When the touch detection is performed, in the self-capacitor screen, the horizontal electrode array and the vertical electrode array are detected in sequence. The horizontal ordinate and the vertical ordinate of the changed capacitor can be determined respectively according to the change of the capacitor before and after touch. Then, the coordinate values of the touch point of the touch screen can be obtained according to the horizontal ordinate and the vertical ordinate of the changed capacitor. According to the self-capacitor scanning mode, the touch point of the touch screen are projected to the X-axis and the Y-axis of a coordinate system respectively, then the coordinate value in the X-axis and the coordinate value in the Y-axis are calculated respectively, and at last the coordinate values of the touch point can be obtained.
If it is single point touch, the projection of the touch point in the X-axis is unique, and the projection thereof in the Y-axis is unique as well. Therefore, the coordinate value of the touch point is unique. However, if there are two touch points in the touch screen, and the two touch points are not located in the same direction along the X-axis or the same direction along the Y-axis, the two touch points have two projections along the X-axis and along the Y-axis respectively. In this case, the coordinate values of four points can be obtained. It is obvious that, only two points in the four points are real, and the other two unreal points are usually referred to as “ghost points.” Consequently, the multi point touch cannot be realized in a self-capacitor screen.
In a mutual capacitor screen, the horizontal electrodes and vertical electrodes (which are made of ITO) are manufactured on the surface of the glass substrate as well. The difference from the self-capacitor screen lies in that, in the mutual capacitor screen, a capacitor would be formed at each of intersection positions of the two groups of electrodes. That is, the two groups of electrodes constitute the two plates of the capacitor respectively. When a finger touches the capacitive screen, the coupling between the two electrodes near the touch point would be affected, and thus the capacitance between the two electrodes would be changed.
When the capacitance of a mutual capacitor is detected, the horizontal electrodes emit scanning signals in sequence. With respect to the scanning signal emitted by each horizontal electrode, all vertical electrodes can receive a corresponding response signal at the same time. In this case, the capacitances of the intersection points of all horizontal electrodes and vertical electrodes, i.e., the capacitance of each detection point in the two-dimensional plane of the whole touch screen, can be obtained. The coordinate values of each touch point can be calculated according to the changing of the capacitance of each detection point in the two-dimensional plane of the touch screen. Therefore, in the mutual capacitor touch screen, the real coordinate values of each touch point can be correctly determined even if there is a plurality of touch points in the screen.
In the mutual capacitor screen, the horizontal electrodes and vertical electrodes can be considered to be arranged in rows and columns on the glass substrate. Since ITO and metal materials which constitute the electrodes all have a certain resistance, and there also exists influences of other factors in the structure, different degrees of attenuation would be generated during a process when the signal transmits between each horizontal electrode and a corresponding vertical electrode. The attenuation would interfere in the following touch detection and detection algorithm. Therefore, not only the complexity of the detection algorithm would be increased to a large extent, but also misdetection would possibly be resulted in.